Batteries (cells) that generate electric power through physical or chemical reaction to supply the generated power to the outside are used when AC power to be supplied to the building is not obtained, or DC power is required according to the living environments surrounded by various electric and electronic devices.
Among such batteries, primary batteries and secondary batteries, which are chemical batteries using chemical reaction, are being generally used. The primary batteries are consumable batteries which are collectively referred to as dry batteries. Also, secondary batteries are rechargeable batteries that are manufactured by using a material in a redox process between current and a substance is repeatable several times. When the reduction reaction is performed on the material by the current, power is charged, and when the oxidation reaction is performed on the material, power is discharged. Such the charging-discharging is repeatedly performed to generate electricity.
A lithium ion battery of the secondary batteries is manufactured through the following processes. An active material is applied to each of a positive electrode conductive foil and a negative electrode conductive foil at a predetermined thickness, and a separator is disposed between the positive electrode conductive foil and the negative electrode conductive foil, and then, an electrode assembly, in which the positive electrode conductive foil, the separator, and the negative electrode conductive foil are wound several times in a jelly-roll or cylindrical shape, is accommodated into a cylindrical or prismatic can, a pouch, and the like to seal the resultant product, thereby manufacturing the lithium ion battery.
A pouch type secondary battery and a method for sealing a pouch are disclosed in Korea Patent Publication No. 10-2014-0004305.
According to the related art, a pouch for a secondary battery is manufactured by sequentially stacking an exterior, aluminum (Al), and an interior.
However, the pouch for the secondary battery has a problem that the more a degree of charging increases, the more thermal stability decreases.
That is, when the battery is verified through a thermal safety test, if the charged battery (SOC 100) is exposed to a temperature higher than room temperature, a thermal runaway phenomenon may occur to cause ignition of the battery.
Particularly, a pouch type battery which does not include a safety mechanism such as a positive temperature coefficient (PTC) or a low-voltage current interrupt device (CID) has a problem that such a phenomenon easily occurs.